This image shows an aerial view of the Chajnantor Plateau, located at an altitude of 5000 meters in the Chilean Andes, where the array of ALMA antennas is located. Credit: Clem & Adri Bacri-Normier (wingsforscience.com)/ESO.
A new film called The View From Mars takes a look ALMA (Atacama Large Millimeter Array), the huge international telescope project that was inaugurated in Chile this week. It is located in the Atacama Desert, the driest place on Earth and an area that bears a striking resemblance to the Red Planet.
But the conditions there, with clear, dry skies, are perfect for astronomy. ALMA’s moveable group of 66 giant antennas do not detect visible light like conventional optical telescopes. Instead they work together to gather emissions from gas, dust and stars and make observations in millimeter wavelengths, using radio frequencies instead of visible light—with no need for darkness, so the stars can be studied around the clock. With these tools, astronomers will soon be able to look billions of years into the past, gazing at the formation of distant stars and galaxies.
“In doing so,” says filmmaker Jonathan de Villiers, “they’ll build a clearer picture of how our sun and our galaxy formed.”
This image shows an aerial view of the Chajnantor Plateau, located at an altitude of 5000 meters in the Chilean Andes, where the array of ALMA antennas is located. Credit: Clem & Adri Bacri-Normier (wingsforscience.com)/ESO.
Today, in a remote part of the Chilean Andes, the Atacama Large Millimeter/submillimeter Array (ALMA), was inaugurated at an official ceremony. This event marks the completion of all the major systems of the giant telescope and the formal transition from a construction project to a fully fledged observatory. ALMA is a partnership between Europe, North America and East Asia in cooperation with the Republic of Chile.
ALMA is able to observe the Universe by detecting light that is invisible to the human eye, and will show us never-before-seen details about the birth of stars, infant galaxies in the early Universe, and planets coalescing around distant suns. It also will discover and measure the distribution of molecules — many essential for life — that form in the space between the stars.
ALMA’s three international partners today welcomed more than 500 people to the ALMA Observatory in the Chilean Atacama Desert to celebrate the success of the project. The guest of honour was the President of Chile, Sebastián Piñera.
In honor of the official inauguration of ALMA, this movie, called ALMA — In Search of Our Cosmic Origins, has been released:
The President of Chile, Sebastián Piñera, said: “One of our many natural resources is Chile’s spectacular night sky. I believe that science has been a vital contributor to the development of Chile in recent years. I am very proud of our international collaborations in astronomy, of which ALMA is the latest, and biggest outcome.”
The Director of ALMA, Thijs de Graauw, expressed his expectations for ALMA. “Thanks to the efforts and countless hours of work by scientists and technicians in the ALMA community around the world, ALMA has already shown that it’s the most advanced millimetre/submillimetre telescope in existence, dwarfing anything else we had before. We are eager for astronomers to exploit the full power of this amazing tool.”
The observatory was conceived as three separate projects in Europe, USA and Japan in the 1980s, and merged to one in the 1990s. Construction started in 2003. The total construction cost of ALMA is approximately US$ 1.4 billion.
The antennas of the ALMA array, fifty-four 12-metre and twelve smaller 7-meter dish antennas, work together as a single telescope. Each antenna collects radiation coming from space and focuses it onto a receiver. The signals from the antennas are then brought together and processed by a specialized supercomputer: the ALMA correlator. The 66 ALMA antennas can be arranged in different configurations, where the maximum distance between antennas can vary from 150 meters to 16 kilometers.
Fomalhaut's exoplanet (NASA, ESA, P. Kalas (UC, Berkeley))
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The planetary system of the star Fomalhaut has been one of intense debate over the past few years. In 2008, it was announced that a large, Saturn mass planet shepherd a large dust ring and was spotted in visual images from Hubble. But in late 2011 infrared observations called the previous detections into question. Now joining the discussion is the recently completed Atacama Large Millimeter/sub-millimeter Array (ALMA). This radio observatory suggests that there may be more planets than previously detected.
ALMA sits in the high Atacama desert in northern Chile. This dry location is ideal for linking together the 66 radio dishes (although only 15 were used in the new observations) to give unprecedented resolution. With this new set of eyes, astronomers from the University of Florida and Bryant Space Science Center were able to study the fine details in the dust ring. These details were then compared to various models of how rings should function in different conditions.
The dust ring has several characteristics that any explanation would have to reproduce. The first was that the ring is slightly oval shaped. It must be exceptionally thin and have a sharp cutoff both on the interior and exterior edges. If the previously claimed planet, Fomalhaut b, were the only one present, it could not account for the outer edge of the disk being sharply truncated as well as the inner edge. Another possibility is that the ring is simply newly formed as the result of a collision between two planets and has not yet had time to dissipate giving it the sharp appearance. However, the authors note that planets at such a distance from the parent star shouldn’t have high enough relative velocities to crush them so finely.
Since neither of these explanations are sufficient, the team proposes that there are two planets that shepherd the ring: One interior and one exterior to it. Within our own solar system, we see similar effects in Uranus’ ε ring which is constrained by the moons Cordelia and Ophelia. Similarly, Saturn’s F ring is shepherded by Prometheus and Pandora. By varying the mass of hypothetical planets in the models, the authors could create a ring similar to that seen around Fomalhaut. However, the best fit was created by a pair of planets that were less than three times the mass of the Earth which would mean that the proposed mass for Fomalhaut b was significantly too high, further casting doubt on its existence. Additionally, the proposed orbit of Fomalhaut bwas 10 AU off from the orbit of the hypothetical interior shepherd planet.
Ultimately, these two planets are only hypothetical. Detecting them in a more direct fashion will prove challenging. The fact that their orbits wouldn’t be very close to line of sight as well as their distance from the star would make radial velocity detection impossible. Given the low proposed mass and the distance, they would reflect too little light to be able to be directly observed with current telescopes.
ALMA's first light: a view of the Antennae Galaxies. Credit: ESO
There’s a new telescope in town that just opened up for business. It’s the long awaited ALMA, the Atacama Large Millimeter/submillimeter Array. Although it is still under construction, the science teams have released the first “early science” image, showing a pair of interacting galaxies called the Antenna Galaxies. ALMA’s view reveals a part of the Universe that just can’t be seen by visible-light and infrared telescopes. “From the formation of the first galaxies, stars, and planets to the merging of the first complex molecules, the science of ALMA is a vast spectrum of investigation,” said Tania Burchell, the ALMA Public Information Officer at the National Radio Astronomy Observatory, on today’s 365 Days of Astronomy podcast.
A composite image combining images of the Antenna Galaxies from ALMA and the Hubble Space Telescope. Credit: ESO, Space Science Institute
Currently, about one third of ALMA’s eventual 66 radio antennas are built and operational. The antennas are positioned just 125 meters apart on the Chajnantor plateau in northern Chile. This extremely dry and high desert sits over 5,000 meters (16,500) feet above sea level. This puts ALMA higher than any other telescope array on Earth. At this elevation, the temperatures hover around freezing all year round, and the air pressure is half that at sea level. Cold temperatures combined with little air is perfect for telescopes like ALMA.
“Even in this very early phase ALMA already outperforms all other submillimetre arrays,” said Tim de Zeeuw, Director General of ESO, the European partner in ALMA. “Reaching this milestone is a tribute to the impressive efforts of the many scientists and engineers in the ALMA partner regions around the world who made it possible.”
Historically, collecting, focusing, and imaging millimeter and submillimeter waves has been very tricky, Burchell said.
“These waves are so large that mirrors cannot focus them, and their frequencies are too high for off-the-shelf receiver technologies to process,” said said. “The warmth of a telescope’s own electronics is enough to ruin the weak cosmic mm signals that, by the time they reach us, sputter in at about a billionth of a billionth the power of a cell phone call. And as an added torment, humidity itself broadcasts at these frequencies, turning most skies into a glare of millemeter/submillimeter light.”
But ALMA is radically different from visible-light and infrared telescopes. It is an array of linked antennas acting as a single giant telescope, and it detects much longer wavelengths than those of visible light. Its images therefore look quite unlike more familiar pictures of the cosmos.
Compare images of the Antenna Galaxies, from ALMA and the Very Large Telescope:
A comparison of the views of the Antenna Galaxies, from ALMA and the VLT. Credit: ESO.
ALMA’s view reveals the clouds of dense cold gas from which new stars form. This is the best submillimeter-wavelength image ever made of the Antennae Galaxies.
Massive concentrations of gas are found not only in the hearts of the two galaxies but also in the chaotic region where they are colliding. Here, the total amount of gas is billions of times the mass of our Sun — a rich reservoir of material for future generations of stars. Observations like these open a new window on the submillimetre Universe and will be vital in helping us understand how galaxy collisions can trigger the birth of new stars. This is just one example of how ALMA reveals parts of the Universe that cannot be seen with visible-light and infrared telescopes.
The ALMA telescope located high in the Chilean Andes made its first measurements on Tuesday using just two of the eventual 66 antennas that will comprise the array. The Atacama Large Millimeter/submillimeter Array took interferometric measurements of radio signals, or “fringes,” from a distant quasar (3C454.3) at sub-millimeter wavelengths. Astronomers said the data from the two 12-meter antennas provided unprecedented sensitivity and resolution, and observations at a wavelength of less than 1mm showed ALMA was now truly a “submillimeter” as well as millimeter-wave telescope.
ALMA is the largest, most ambitious ground-based observatory ever created, with completion slated for 2012. When all 66 antennas are working in synch, researchers believe ALMA will revolutionize the way we see the universe, probing deep into some of the first galaxies to form after the Big Bang and observing planets in mid-formation around young stars.
Interferometry involves linking together arrays of smaller telescopes to make measurements of an object. Sophisticated electronic systems will correlating the signals.
The next step in the process will be the addition of a third antenna which will allow the Alma team to obtain “phase closure.” This is an important capability which requires at least three antennas to cancel out errors in the “phase” of the signals caused by the instruments themselves and by the Earth’s atmosphere.
